From nobody Mon Feb 9 08:55:52 2026 Delivered-To: importer@patchew.org Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zohomail.com; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail(p=none dis=none) header.from=virtuozzo.com ARC-Seal: i=1; a=rsa-sha256; t=1579540968; cv=none; d=zohomail.com; s=zohoarc; b=nZ1bDoTIeyQ/PUlc1wkfYxuzdkSYKbDQJ7/e7+91leiWqNGHi5NndBtS0lfnoai5hWxWuHyySh0LMJFjGh9QBWwtwVEI6A58q9cgyh20TvLDXxLNWdNSOOU46Q8dXUYaw1pcxKNUgcjeGamvVYGHOnZuBEojul1miAkmo2b4qzk= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.com; s=zohoarc; t=1579540968; h=Content-Transfer-Encoding:Cc:Date:From:In-Reply-To:List-Subscribe:List-Post:List-Id:List-Archive:List-Help:List-Unsubscribe:MIME-Version:Message-ID:References:Sender:Subject:To; bh=WO8kNTYxYFxfKcT9JhL/9gTG+HbrKUbbdsUDuzUP01A=; b=MvJaF3s2KxjiWsQXalPCsHM4yW67Nrhq2q+P/mpYo1BelKi0lOlgQm8NqdqXKw8UEiHLAkTIde8zmbUYCDooHF67ADdUtBDUbe0OUPXOPU95Rn3F1wLYNepyB/6W8+QMTYLcm64sDkuWgn2c3X6JbpbMsh8SenxnpRLVweCaHgk= ARC-Authentication-Results: i=1; mx.zohomail.com; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; dmarc=fail header.from= (p=none dis=none) header.from= Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1579540968382489.8890578048771; Mon, 20 Jan 2020 09:22:48 -0800 (PST) Received: from localhost ([::1]:40510 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1italD-00066B-3W for importer@patchew.org; Mon, 20 Jan 2020 12:22:47 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:37021) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1itacz-0005W0-4g for qemu-devel@nongnu.org; Mon, 20 Jan 2020 12:14:18 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1itacx-0004SY-Ta for qemu-devel@nongnu.org; Mon, 20 Jan 2020 12:14:16 -0500 Received: from relay.sw.ru ([185.231.240.75]:37530) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1itacu-0004R9-GU; Mon, 20 Jan 2020 12:14:12 -0500 Received: from vovaso.qa.sw.ru ([10.94.3.0] helo=kvm.qa.sw.ru) by relay.sw.ru with esmtp (Exim 4.92.3) (envelope-from ) id 1itact-0002hc-0z; Mon, 20 Jan 2020 20:14:11 +0300 From: Vladimir Sementsov-Ogievskiy To: qemu-block@nongnu.org Subject: [PATCH v10 2/2] docs: qcow2: introduce compression type feature Date: Mon, 20 Jan 2020 20:13:45 +0300 Message-Id: <20200120171345.24345-3-vsementsov@virtuozzo.com> X-Mailer: git-send-email 2.21.0 In-Reply-To: <20200120171345.24345-1-vsementsov@virtuozzo.com> References: <20200120171345.24345-1-vsementsov@virtuozzo.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [fuzzy] X-Received-From: 185.231.240.75 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: kwolf@redhat.com, vsementsov@virtuozzo.com, armbru@redhat.com, qemu-devel@nongnu.org, dplotnikov@virtuozzo.com, den@openvz.org, mreitz@redhat.com Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" Content-Type: text/plain; charset="utf-8" The patch add new additional field to qcow2 header: compression_type, which specifies compression type. If field is absent or zero, default compression type is set: ZLIB, which corresponds to current behavior. New compression type (ZSTD) is to be added in further commit. Suggested-by: Denis Plotnikov Signed-off-by: Vladimir Sementsov-Ogievskiy --- docs/interop/qcow2.txt | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/docs/interop/qcow2.txt b/docs/interop/qcow2.txt index 355925c35e..4569f0dba3 100644 --- a/docs/interop/qcow2.txt +++ b/docs/interop/qcow2.txt @@ -109,6 +109,11 @@ the next fields through header_length. An External Data File Name header extensio= n may be present if this bit is set. =20 + Bit 3: Compression type bit. If this bit is set, + a non-default compression is used for comp= ressed + clusters. The compression_type field must = be + present and not zero. + Bits 3-63: Reserved (set to 0) =20 80 - 87: compatible_features @@ -189,7 +194,16 @@ present*, if not altered by a specific incompatible bi= t. *. A field is considered not present when header_length is less or equal t= o the field's offset. Also, all additional fields are not present for version 2. =20 - < ... No additional fields in the header currently ... > + 104: compression_type + Defines the compression method used for compressed clu= sters. + All compressed clusters in an image use the same compr= ession + type. + If the incompatible bit "Compression type" is set: the= field + must be present and non-zero (which means non-zlib + compression type). Otherwise, this field must not be p= resent + or must be zero (which means zlib). + Available compression type values: + 0: zlib =20 =20 =3D=3D=3D Header padding =3D=3D=3D --=20 2.21.0